Compressor diffuser having vanes with variable cross-sections

ABSTRACT

A diffuser is disclosed for use with a compressor. The compressor diffuser may have a ring-shaped generally flat plate, a plurality of first vanes disposed radially around an upper surface of the plate, and a plurality of second vanes shorter than the first vanes. Each of the second vanes may be connected to the plate between adjacent first vanes. The first and second vanes may each have a high-pressure side and an opposing low-pressure side, and each may tilt towards one of its corresponding high- and low-pressure sides at a lean angle that changes along its meridional length.

TECHNICAL FIELD

The present disclosure is directed to a diffuser and, more particularly, to a compressor diffuser having vanes with variable cross-sections.

BACKGROUND

Internal combustion engines such as, for example, diesel engines, gasoline engines, and gaseous fuel powered engines are supplied with a mixture of air and fuel for subsequent combustion within the engines that generates a mechanical power output. In order to maximize the power generated by this combustion process, each engine can be equipped with a turbocharged air induction system.

A turbocharged air induction system includes a turbocharger that uses exhaust from the engine to compress air flowing into the engine, thereby forcing more air into a combustion chamber of the engine than the engine could otherwise draw into the combustion chamber. This increased supply of air allows for increased fuelling, resulting in an increased power output. A turbocharged engine typically produces more power than the same engine without turbocharging. A conventional turbocharger includes a compressor housing, a centrifugal compressor wheel centrally disposed within the housing and driven to rotate by a connected turbine wheel, and a stationary diffuser (vaned or vaneless) situated at a peripheral outlet of the compressor wheel. A vaned diffuser is typically ring-shaped and includes protruding vanes that are angled relative to a radial flow path of air exiting blades of the compressor wheel. The vanes in the diffuser create restricted passages for the air that cause the air to slow down, trading velocity for an increase in pressure.

An exemplary compressor diffuser is disclosed in U.S. Pat. No. 5,178,516 of Nakagawa et al. that issued on Jan. 12, 1993 (the '516 patent). Specifically, the '516 patent describes a vaned diffuser having a plurality of stator blades radially arranged around the periphery of a compressor wheel, and a plurality of smaller auxiliary blades interleaved with the stator blades. The auxiliary and stator blades are curved along their length and have vertical walls that extend orthogonally between a hub surface of the diffuser and a mating shroud.

Although the diffuser of the '516 patent may be adequate for some applications, it may still be less than optimal. In particular, because the blades of the '516 patent have orthogonal walls, the channels between the blades formed by the walls of the blades have generally rectangular cross-sections. This cross-sectional shape may allow for a non-uniform distribution of airflow, pressure, and velocity within the channels, and such distributions can result in a reduced efficiency and/or range of the associated turbocharger.

The diffuser of the present disclosure solves one or more of the problems set forth above and/or other problems of the prior art.

SUMMARY

In one aspect, the present disclosure is directed to a compressor diffuser. The compressor diffuser may include a ring-shaped generally flat plate, a plurality of first vanes disposed radially around an upper surface of the plate, and a plurality of second vanes shorter than the first vanes. Each of the second vanes may be connected to the plate between adjacent first vanes. The first and second vanes may each include a high-pressure side and an opposing low-pressure side. Each of the first and second vanes may tilt towards one of its corresponding high- and low-pressure sides at a lean angle that changes along its meridional length.

In another aspect, the present disclosure is directed to another compressor diffuser. This compressor diffuser may include a ring-shaped generally flat plate, a plurality of first vanes disposed radially around an upper surface of the plate, and a plurality of second vanes shorter than the first vanes. Each of the second vanes may be connected to the plate between adjacent first vanes. A density of the first and second vanes may vary relative to an annular position around the plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial illustration of an exemplary disclosed engine;

FIG. 2 is a cross-sectional illustration of an exemplary disclosed turbocharger that may be used in conjunction with the engine of FIG. 1;

FIG. 3 is a pictorial illustration of an exemplary disclosed diffuser that may be used in conjunction with the turbocharger of FIG. 2;

FIG. 4 is a pictorial illustration of exemplary disclosed vanes that may be used in conjunction with the diffuser of FIG. 3; and

FIGS. 5 and 6 are charts associated with exemplary disclosed geometry of the vanes of FIG. 4.

DETAILED DESCRIPTION

FIG. 1 illustrates an engine 10 equipped with an air induction system 12 and an exhaust system 14. For the purposes of this disclosure, engine 10 is depicted and described as a two-stroke diesel engine. One skilled in the art will recognize, however, that engine 10 may be another type of internal combustion engine such as, for example, a two- or four-stroke gasoline or gaseous fuel-powered engine. Engine 10 may include an engine block 16 that at least partially defines a plurality of cylinders 18. A piston (not shown) may be slidably disposed within each cylinder 18 to reciprocate between a top-dead-center position and a bottom-dead-center position, and a cylinder head (not shown) may be associated with each cylinder 18.

Cylinder 18, the piston, and the cylinder head may form a combustion chamber. In the illustrated embodiment, engine 10 includes twenty such combustion chambers arranged in two separate banks (only one shown in FIG. 1). However, it is contemplated that engine 10 may include a greater or lesser number of combustion chambers and that the combustion chambers may be disposed in an “in-line” configuration, in a “V” configuration, in an opposing piston configuration, or in any other suitable configuration.

Air induction system 12 may include components configured to introduce charged air into the combustion chambers of engine 10. For example, air induction system 12 may include an induction manifold (not shown—located between the opposing banks of combustion chambers) fluidly connected along its length to the combustion chambers, one or more compressors 24 in fluid communication with an end of the induction manifold, and, in some embodiments, an air cooler (not shown) located downstream of compressors 24 and upstream of the combustion chambers. It is contemplated that additional components may be included within air induction system 12, if desired, such as valving, one or more air cleaners, one or more waste gates, a control system, a bypass circuit, and other means for introducing charged air into engine 10. It is also contemplated that the air cooler may be omitted, if desired.

Each compressor 24 of engine 10 may embody a fixed geometry centrifugal-type compressor that is mechanically driven to compress air flowing into engine 10 to a predetermined pressure level. Compressors 24, if more than one is included within air induction system 12, may be disposed in a series or parallel relationship and fluidly connected to engine 10 via the induction manifold.

Exhaust system 14 may be configured to recuperate energy from the exhaust flowing out of the combustion chambers of engine 10. For example, exhaust system 14 may include an exhaust manifold 26 fluidly connected along its length to the combustion chambers, and one or more turbines 28 in fluid communication with an end of exhaust manifold 26. Turbines 28, if more than one is included within exhaust system 14, may be connected in a series or parallel relationship.

Each turbine 28 of exhaust system 14 may be mechanically connected to one or more compressors 24 of air induction system 12 to form a turbocharger 30. Turbocharger 30 may be mounted to engine 10 by way of a housing 32. As the hot exhaust gases exiting engine 10 move through exhaust manifold 26 into turbine 28 and expand against blades thereof, turbine 28 may rotate and drive the connected compressors 24 to compress inlet air directed to the combustion chambers of engine 10 via the induction manifold.

As illustrated in FIG. 2, compressor 24 and turbine 28 may each include an associated shroud 34, 36 configured to house corresponding compressor and turbine wheels 38, 40 that are connected to each other via a common shaft 42. Each shroud 34, 36 may generally include an inlet 44, an outlet 46, and a scroll 48 connecting inlet 44 to outlet 46. Inlets 44 may be axially oriented, while outlets 46 may be radially oriented. In particular, as compressor wheel 38 is rotated, air may be drawn axially in toward a center of compressor wheel 38. Blades 49 of compressor wheel 38 may then push the air radially outward in a spiraling fashion through scroll 48 and into the induction manifold (referring to FIG. 1). Similarly, as exhaust from exhaust manifold 26 is directed axially inward to turbine wheel 40, the exhaust may push against blades 50 of turbine wheel 40 causing turbine wheel 40 to rotate and drive compressor wheel 38 via shaft 42. After passing through turbine wheel 40, the exhaust may spiral radially outward through outlet 46. Compressor and turbine wheels 38, 40 may embody conventional wheels, with any number and configuration of blades 49, 50 radially disposed on a pressure face of corresponding wheel bases.

Shroud 34 associated with compressor 24 may include a diffuser 52 located within the outward radial flow path at a periphery of compressor wheel 38. As can be seen in FIG. 3, diffuser 52 may include, among other things, a ring-shaped generally flat plate 54 having a plurality of main vanes 56 and a plurality of splitter vanes 58. As shown in FIG. 4, each of main and splitter vanes 56, 58 may include a lower face (also known as a hub face) 60 that is connected to plate 54, an opposing upper face (also known as a shroud face) 62 that engages an inner surface of shroud 34, a leading edge 64 located close to compressor wheel 38, an opposing a trailing edge 66 located away from compressor wheel 38, a low-pressure side (also known as the suction side) 68, and an opposing high-pressure side (also known as the pressure side) 70.

For the purposes of this disclosure, a height H of main and splitter vanes 56, 58 may refer to an orthogonal distance between lower and upper faces 60, 62. A chord length L_(c) (shown in FIG. 3) may refer to a straight line distance between leading and trailing edges 64, 66. A meridional length L_(M) (shown in FIG. 3) may refer to a distance between leading and trailing edges 64, 66 of main and splitter vanes 56, 58 along a camber line passing through a lengthwise center of the respective vanes. A thickness T may refer to a distance between low- and high-pressure sides 68, 70 that is generally orthogonal to the curving line. A spacing S (shown in FIG. 3) may refer to a straight line distance between adjacent trailing edges 66 (e.g., a spacing of main vanes 56 may refer to the straight line distance between trailing edges 66 of adjacent main vanes 56). A solidity ratio SR may be defined as the ratio of the chord length L_(C) to the spacing S (SR=L/S). An elliptical ratio of main and splitter vanes 56, 58 may be defined as the ratio of the focal length of the elliptical shape at leading edge 64 or trailing edge 66 divided by one-half of the width of the elliptical shape at a point of tangency with low- and high-pressure sides 68, 70.

The disclosed geometry of main and splitter vanes 56, 58 has been selected to provide a desired flow uniformity through diffuser 52 that results in improved efficiency and range of turbocharger 30. For example, splitter vanes 58 are shorter than main vanes 56. Leading edges 64 of splitter vanes 58 are located radially outward of leading edges 64 of main vanes 56 (e.g., at a radial location that is about 25-55% of the meridional length L_(M) of main vanes 56 from leading edge 64 to trailing edge 66), and trailing edges 66 are generally radially aligned. One splitter vane 58 may be located between adjacent main vanes 56 (i.e., between the low-pressure side 68 of one main vane 56 and the high-pressure side 70 of an adjacent main vane 56) and closer to the high-pressure side 70 than to the low-pressure side 68. That is, splitter vanes 58 may be asymmetrically located relative to main vanes 56, although the asymmetry should be capped at about 5% relative to a center line located halfway between the adjacent main vanes 56. The solidity ratio of main and splitter vanes 56, 58 may be about 0.7-1.4, with about 8 to 18 pairs of vanes 56, 58. In this arrangement, plate 54 may have a ring ratio (i.e., ratio of outer diameter to inner diameter) of about 1.3-1.6.

It is contemplated that the annular density of main and splitter vanes 56, 58 may also be asymmetric, if desired. For example, it may be beneficial in some applications to have a greater density of main and splitter vanes 56, 58 attached to plate 54 at an annular region corresponding with a tongue (i.e., the smallest diameter entrance) of scroll 48 near an outlet cone of scroll 48. The tongue of scroll 48 may be known to cause flow disruption (e.g., turbulence), and the higher density of vanes in this area may help to improve a uniformity of the flow. It may also be beneficial to have asymmetric annular density for different pairs of main and splitter vanes 56, 58 to reduce resonance vibration characteristics of turbocharger 30.

Leading and trailing edges 64, 66 of main and/or splitter vanes 56, 58 may be rounded or tapered. In the disclosed embodiment, leading edges 64 may have an elliptical shape, with a leading edge elliptical ratio of about 2-6:1 for main vanes 56 and about 4-10:1 for splitter vanes 58. In this same embodiment, trailing edges 66 may also have an elliptical shape, with a trailing edge elliptical ratio of about 2-4:1. The elliptical ratios for both main and splitter vanes 56, 58 may increase within the vanes accordingly to a height of the vanes between hub face 60 and shroud face 62 (i.e., main and splitter vanes 56, 58 may have leading and/or trailing edges 64, 66 that become narrower at shroud faces 62).

Main and splitter vanes 56, 58 may tilt toward one of their corresponding low- and high-pressure sides 68, 70, such that a cross-section of channels formed between these vanes is generally oblique and/or irregular. As shown in the exemplary embodiment of FIG. 4, main and splitter vanes 56, 58 tilt toward their respective low-pressure sides 68, with a lean angle α (the interior angle that main and splitter vanes 56, 58 make in a height direction relative to an upper planar surface of plate 54) that varies along the meridional length L_(M). Main and splitter vanes 56, 58 may also curve along their lengths, each forming a corresponding meridional vane angle β (i.e., angle formed between a radial line drawn from a center of plate 54 to a corresponding tangent on the camber line of the vane). Meridional vane angle β, like lean angle α, may change along the meridional length L_(M), as well as along the height H of main and splitter vanes 56, 58, and have an absolute value within the range of about 36-76 degrees. Specifically, FIG. 5 shows a first curve 500 corresponding to the meridional vane angle β at hub face 60, and a second curve 510 corresponding to the meridional vane angle β at shroud face 62. As can be seen from a comparison of first and second curves 500, 510, the meridional vane angle at shroud face 62 may generally be larger than the meridional vane angle β at hub face 60 (i.e., main and splitter vanes 56, 58 may be more vertical at shroud face 62). The distribution may alternatively be such that the meridional vane angle β is larger at hub face 60, if desired. In addition, the meridional vane angle α at shroud face 62 may generally mirror the meridional vane angle β at hub face 60, with the meridional vane angle β at both faces reaching a maximum at about 15-20% of the meridional length L_(M) from leading edge 64 to trailing edge 66 and a minimum at a trailing edge 66. Finally, the meridional vane angle β for main vanes 56 may be about the same as the meridional vane angle β for splitter vanes 58, relative to the percent of the meridional length L_(M) from leading edge 64 to trailing edge 66 of the respective vanes. In other words, the meridional vane angle β of main vanes 56 at about 50% of their meridional length L_(M) from leading edge 64 to trailing edge 66 may be about the same as the meridional vane angle β of splitter vanes 58 at about 50% of the meridional length L_(M) of main vanes 56.

As shown in FIG. 6, the thickness T of main and splitter vanes 56, 58 may also vary along their meridional length L_(M). In particular, FIG. 6 shows a curve 600 corresponding to the thickness T of main and splitter vanes 56, 58 relative to the meridional length L_(M) of main vanes 56. As can be seen from curve 600, the thickness of main and splitter vanes 56, 58 may reach a maximum at about 25-40% of the meridional length L_(M) and be thinnest at trailing edge 66. The thickness T of main vanes 56 may be about the same as the thickness T of splitter vanes 58, relative to the percent of the meridional length L_(M) from leading edge 64 to trailing edge 66 of main vanes 56.

INDUSTRIAL APPLICABILITY

The disclosed diffuser may be implemented into any turbocharger and power system application where increased efficiency and range is desired. In particular, the disclosed geometry of main and splitter vanes 56, 58 may be selected to improve flow uniformity, choke margin, and surge margin. Improved flow uniformity may result in a greater flow rate of compressed air with fewer losses.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed diffuser. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed diffuser. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents. 

What is claimed is:
 1. A compressor diffuser, comprising: a ring-shaped generally flat plate; a plurality of first vanes disposed radially around an upper surface of the plate; and a plurality of second vanes shorter than the first vanes, each of the second vanes being connected to the plate between adjacent first vanes, wherein: each of the first and second vanes includes a high-pressure side and an opposing low-pressure side; and each of the first and second vanes tilts towards one of its corresponding high- and low-pressure sides at a lean angle that changes along its meridional length.
 2. The compressor diffuser of claim 1, wherein each of the first and second vanes have a vane angle that also changes along its meridional length, with an absolute value a range of about 36-76 degrees.
 3. The compressor diffuser of claim 2, wherein the vane angle is greatest for the first vanes at about 15-20% of a meridional length from a leading edge to a trailing edge.
 4. The compressor diffuser of claim 3, wherein the vane angle is lowest for the first vanes at the trailing edge.
 5. The compressor diffuser of claim 2, wherein the vane angles associated with the first and second vanes relative to a percent of meridional length of the first vanes are about the same.
 6. The compressor diffuser of claim 2, wherein the vane angles associated with the first and second vanes also vary along a height of the first and second vanes between a hub face and a shroud face.
 7. The compressor diffuser of claim 6, wherein the vane angles are greatest at one of the hub face or shroud face.
 8. The compressor diffuser of claim 1, wherein leading edges of the second vanes are located radially outward of leading edges of the first vanes.
 9. The compressor diffuser of claim 8, wherein the leading edges of the second vanes are located at a radial position corresponding to about 25-55% of a meridional length of the first vanes.
 10. The compressor diffuser of claim 9, wherein trailing edges of the second vanes are located at about the same radial location as trailing edges of the first vanes.
 11. The compressor diffuser of claim 1, wherein at least one of the second vanes is located asymmetrically between adjacent first vanes.
 12. The compressor diffuser of claim 11, wherein each of the second vanes is located within about 5% of a line of symmetry located between adjacent first vanes.
 13. The compressor diffuser of claim 1, wherein a density of the first and second vanes varies relative to an annular position around the plate.
 14. The compressor diffuser of claim 13, wherein a greater density of the first and second vanes is located at a region of the plate corresponding with a tongue of a shroud scroll.
 15. The compressor diffuser of claim 1, wherein each of the first and second vanes includes a generally tapered trailing edge and a generally rounded leading edge.
 16. The compressor diffuser of claim 15, wherein a thickness of each of the first and second vanes varies along a meridional length of the first and second vanes.
 17. The compressor diffuser of claim 16, wherein the thickness of each of the first vanes relative to a percent of the meridional length of the first vanes is about the same as the thickness of each of the second vanes relative to a percent of the meridional length of the first vanes.
 18. The compressor diffuser of claim 17, wherein the thickness is greatest at about 25-40% of the meridional length for each of the first vanes.
 19. The compressor diffuser of claim 1, wherein: each of the first vanes includes a hub face and a shroud face; and a solidity ratio of each of the first and second vanes ranges from about 0.7 to 1.4 between the hub face and the shroud face.
 20. The compressor diffuser of claim 1, wherein the first vanes include a leading edge elliptical ratio of about 2-6:1.
 21. The compressor diffuser of claim 20, wherein the second vanes include a leading edge elliptical ratio of about 4-10:1.
 22. The compressor diffuser of claim 21, wherein the leading edge elliptical ratio of at least one of the first vanes and the second vanes increases according to height from a hub face to a shroud face.
 23. The compressor diffuser of claim 21, wherein a trailing edge elliptical ratio of the first and second vanes is about 2-4:1.
 24. A compressor diffuser, comprising: a ring-shaped generally flat plate; a plurality of first vanes disposed radially around an upper surface of the plate; and a plurality of second vanes shorter than the first vanes, each of the second vanes being connected to the plate between adjacent first vanes, wherein a density of the first and second vanes varies relative to an annular position around the plate.
 25. The compressor diffuser of claim 24, wherein a greater density of the first and second vanes is located at a region of the plate corresponding with a tongue of a shroud scroll.
 26. The compressor diffuser of claim 24, wherein: leading edges of the second vanes are located radially outward of leading edges of the first vanes; and trailing edges of the second vanes are located at about the same radial location as trailing edges of the first vanes.
 27. The compressor diffuser of claim 26, wherein leading edges of the second vanes are located at a radial position corresponding to about 25-55% of a meridional length of the first vanes.
 28. The compressor diffuser of claim 24, wherein at least one of the second vanes is located asymmetrically relative to adjacent first vanes.
 29. The compressor diffuser of claim 28, wherein each of the second vanes is located within about 5% of a line of symmetry located between adjacent first vanes.
 30. The compressor diffuser of claim 24, wherein: each of the first and second vanes includes a generally tapered trailing edge and a generally rounded leading edge; and a thickness of each of the first and second vanes varies along a meridional length.
 31. The compressor diffuser of claim 30, wherein a thickness of each of the first vanes relative to a percent of the meridional length of the first vanes is about the same as a thickness of each of the second vanes relative to a percent of the meridional length of the first vanes.
 32. The compressor diffuser of claim 31, wherein the thickness is greatest at about 25-40% of the meridional length for each of the first and second vanes.
 33. The compressor diffuser of claim 24, wherein: each of the first vanes includes a hub face and a shroud face; and a solidity ratio of each of the first and second vanes ranges from about 0.7 to 1.4 along a height from the hub face to the shroud face.
 34. The compressor diffuser of claim 24, wherein: the first vanes include a leading edge elliptical ratio of about 2-6:1; the second vanes include a leading edge elliptical ratio of about 4-10:1; and the first and second vanes include a trailing edge elliptical ratio of about 2-4:1.
 35. The compressor diffuser of claim 34, wherein the leading and trailing edge elliptical ratios of the first and second vanes increases according to height from a hub face to a shroud face.
 36. A turbocharger, comprising: a housing at least partially defining a compressor shroud with a scroll inlet and a turbine shroud with a scroll outlet; a turbine wheel disposed within the turbine shroud; a compressor wheel disposed within the compressor shroud; a shaft connecting the turbine wheel to the compressor wheel; a ring-shaped generally flat plate located at a periphery of the compressor wheel; a plurality of first vanes disposed radially around an upper surface of the plate; and a plurality of second vanes shorter than the first vanes, each of the second vanes being connected to the plate between adjacent first vanes, wherein: the first and second vanes each includes a high-pressure side and an opposing low-pressure side; each of the first and second vanes tilts towards one of the high- and low-pressure sides at a lean angle that changes along its length; each of the first and second vanes has a vane angle that varies along its meridional length and height within a range of absolute values of about 36-76 degrees; and a greater density of the first and second vanes is located at a region of the plate corresponding with a tongue of the scroll inlet of the compressor shroud. 